1. Field of Invention
This invention relates to an electromechanical piezoelectric translation apparatus and, more particularly, to a piezoelectric motor for rotating a shaft formed of hard material which drives a load having a preselected load characteristic and a known friction force which opposes rotation of the shaft and load. The piezoelectric motor includes an annular shaped housing which pivots about a support pin under a clamping force developed by a compliance means to maintain driving contact between the piezoelectric translation apparatus and the shaft.
2. Description of the Prior Art
The concept of a piezoelectric motor or electromechanical device to produce rotational or linear relative movement between an electromechanical device and a driven member is known in the art.
The most pertinent prior art is disclosed is U.S. Pat. No. 4,622,483 entitled PIEZOELECTRIC ELECTROMECHANICAL TRANSLATION APPARATUS AND METHOD and U.S. Pat. No. 4,727,728 entitled PIEZOELECTRIC MULTIAXIS MICROPOSITIONER, both of which have the same inventors as this Application.
U.S. Pat. No. 4,622,483 discloses an electromechanical translation apparatus which is adapted to produce incremental movement relative to a separate member wherein that movement can either be a linear movement or a rotational movement. The electromechanical translation apparatus disclosed in U.S. Pat. No. 4,622,483 includes a housing, a pair of clamping and translating members each of which has driven end and engaging ends wherein each of the engaging ends is adapted to removably clamp and translate separate member relative the housing in response to a driving force which is selectively applied to the clamping and translating members. The engaging ends of the clamping and translating members selectively clamp the separate member at selected locations with a clamping force developed from a compliance means and which varies with the magnitude of the driving force. The electromechanical translation apparatus disclosed in U.S. Pat. No. 4,622,483 includes at least at least one piezoelectric driving element which is operatively coupled to the clamping and translating member. The piezoelectric driving element is capable of being selectively expanded and contracted in a response to a voltage of a selected magnitude and selected frequency. The expansion and contraction of the piezoelectric element produces, between the housing and the clamping and translating members, a variable driving force which varies between a first magnitude and a second magnitude and which enables the engaging ends of the clamping and translating members to apply a variable clamping force to the separate member. A method for producing relative transactional movement between an electromechanical apparatus and a separate member is also disclosed in U.S. Pat. No. 4,622,483. FIGS. 35 and 36 of U.S. Pat. No. 4,622,483 illustrate embodiment of piezoelectric translation apparatus wherein a radially extending housing supports a piezoelectric driving element against a shaft to rotate the same.
U.S. Pat. No. 4,727,278 discloses an electromechanical translation apparatus which is in the form of a piezoelectric multiaxis micropositioner. The apparatus disclosed in U.S. Pat. No. 4,727,278 includes a driven member which is adapted to be incrementally moved in a selected direction, which could be along an "X" axis, along an "XY" axis or "XYZ" axis or in a selected clockwise or counter clockwise direction about a selected axis. The piezoelectric multiaxis micropositioner includes a mounting means, at least three piezoelectric driving assemblies having a housing and an engaging member formed of a hard material having a selected driving end at one end thereof and a driven end at the other end. The engaging member at one end is positioned to selectively engage and translate the driven member in response to a driving force. The piezoelectric multiaxis positioner includes at least three piezoelectric driving elements positioned between a driven end of the engaging member and the housing and wherein the piezoelectric driving elements are positioned in a spaced, angular relationship to each other. Each piezoelectric driving element is capable of separately responding to an electrical signal having a predetermined frequency and amplitude which varies between first polarity and a second polarity to expand and contract to change the geometric dimension of the piezoelectric driving element to apply a driving force on an engaging member. The engaging member imparts an incremental motion to the driven member in a selected direction. The preferred embodiment of the piezoelectric multiaxis positioner disclosed in U.S. Pat. No. 4,727,278, is to incrementally rotate a sphere having an optical element attached thereto for use in optical paths.
Other known piezoelectric electromechanical devices for producing incremental movement are described in U.S. Pat. Nos. 3,138,749; 3,217,218; 3,292,019; 3,377,489; 3,649,856; 3,684,904; 3,902,084; 3,902,085; 4,408,832; 4,422,002; 4,455,501; 4,468,583; and 4,523,120.